UNIO 687 
Margarita (Unio) lecontianus Laas, Syn., 1836, p. 23; 1838, p. 
18. ; 
Unio lecontianus Lea, Tr. Am. Phil. Soc., VI. 1838, p. 40, pl. 
xt 35; Obs., IL, 1838p. 40, pl. x11; fig. 35.— Han ey, 
Div., siells, 1643, p.. 188, pl. xxi, figs. 11, 51—CueEnu;, Il. 
Conch., 1858, pl. xxiv, figs. 6, 6a, 6b—Sowersy, Conch. 
Icon., XVI, 1866, pl. Xxxxi1, fig. 173.—Simpson, Syn., 1900 
P. 733- 
Margaron (Unio) lecontianus Lea, Syn., 1852, p. 26; 1870, p. 
Al. 
More solid, higher in proportion, and having lower, rather 
heavier pseudocardinals and deeper muscle scars than U. gem- 
mus. It seems to stand as a connecting link between that 
species and U/. spissus, in fact all of the species of this group 
are exceedingly close and variable and, although I have not 
seen any great amount of material belonging to it, I have 
, 
found a number of specimens | could not satisfactorily place. 
I formerly thought that U. contrarius Conrad, was a small 
specimen of this with contrary teeth. Since reaching that 
conclusion I have seen material which inclines me to think 
I may have been wrong and I place that species in the genus 
Lampsilis with hesitation. 
Unio spissus Lea. 
Shell subrhomboid or subobovate, being somewhat narrowed 
in front, solid, moderately to greatly inflated, somewhat in- 
equilateral; beaks full and high; posterior ridge high, angled, 
showing a tendency to become double below, ending at or a 
_ little above the base in a blunt point or biangulation; base 
line more or less curved; dorsal line curved; anterior end 
somewhat narrowed and rounded; epidermis brownish-green 
in young shells and sometimes faintly rayed, reddish-brown 
and rayless in old shells: somewhat concentrically sulcated, 
rather dull; pseudocardinals small, compressed, not very per- 
fect in adult shells, often strongly cross-striated, double in each 
valve, the upper one in the right valve small; left valve with 
